The national number of people affected by the listeria outbreak has risen to 17, with the emergence of two more cases this week.

The two cases involved a man from Victoria and a woman from Queensland.

So far, NSW and Victoria saw the highest numbers of cases, with a record of six patients in each state. Queensland followed with four cases, and there has been one in Tasmania.

There have been four deaths, with two deaths in NSW and two in Victoria.

“Listeriosis has a long incubation period- up to 70 days. Therefore there are multiple foods consumed and retailers used by the cases, which need to be thoroughly investigated and the findings matched to specialist laboratory test results, to determine the source,” Director Communicable Diseases NSW Health, Dr Vicky Sheppeard said.

The patients involved in the two cases became ill before contaminated rockmelons were recalled from the market.

Listeriosis may be found in the following foods, and people at risk are encouraged to avoid them.

The people at risk include vulnerable people such as those over 70, pregnant, diabetic, and have suppressed immune systems. Listeriosis can be extremely serious or even life threatening for these groups of people.

“Typically around one third of people who fall ill with listeriosis die every year. Most of the cases are never related to an outbreak like this one we’re seeing with the rockmelon contamination,” Dr Sheppeard said.